The cerebral vascular system serves constant demand of neuronal activities in the brain. Neural activations are typically followed by immediate rise in local blood flow through neural-vascular coupling. Temporal dynamics and spatial redistribution of this hyperemia within the capillary bed play a deterministic role in oxygen diffusing capacity, however, the functional behavior of which remains poorly understood. Taking the advantages of the high spatiotemporal resolution of OCT velocimetry designed upon eigen-decomposition (ED) statistical analysis, we investigated the intrinsic capillary red blood cell (RBC) fluctuations within mouse cerebral cortex, representing as bandwidths of the RBC flow frequencies. The temporal hemodynamics before (rest) and during (activation) a bout of hindpaw electrical stimulations are accordingly analyzed to resolve alterations in capillary flow disturbance and its spatial distribution. In our experiment, the electrical stimulation provokes a temporal RBC fluctuation increase (rest: 16715 m/s; activation: 20516 m/s; P < 0.05) in the capillary bed located in hindpaw somatosensory cortex (HSC), as compared to the control (rest: 17020 m/s; activation: 16918 m/s; P > 0.05) ; accompanied with an increase in capillary RBC velocity (rest: 49640 m/s; activation: 61349 m/s; P < 0.05) in HSC, as compared to the control (rest: 54462 m/s; activation: 55868 m/s; P > 0.05). In addition, no significant difference was observed for the capillary vessel density in either HSC (rest: 0.390.02 m/s; activation: 0.370.01 m/s; P > 0.05) or control (rest: 0.360.02 m/s; activation: 0.370.02 m/s; P > 0.05). We conclude that neural activation evokes spatiotemporal redistribution of capillary hemodynamics regulated through instantaneous increments in flow disturbance and flow velocity, but involves no recruitment of reserved capillaries (no RBC transit path variation). Our demonstration shows the potential of OCT angiography for functional investigation and modeling of spatiotemporally coupled hemodynamics to neural activities.
Wei Wei, Yuandong Li, and Ruikang K. Wang, "OCT velocimetry reveals electrical-evoked temporal capillary hemodynamics in mouse cerebral cortex during functional activation (Conference Presentation)," Proc. SPIE 10493, Dynamics and Fluctuations in Biomedical Photonics XV, 104930L (Presented at SPIE BiOS: January 29, 2018; Published: 15 March 2018); https://doi.org/10.1117/12.2290590.5752217059001.
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